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Observing >> Deep Sky Observing

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JasonBurry
sage


Reged: 04/27/12

Loc: Cape Spencer, NB, Canada
Re: Pleaides Nebulosity new [Re: Dave Mitsky]
      #5564281 - 12/10/12 02:26 PM

I see the Merope nebula fairly regularly from my blue/green back yard. Living adjacent to a large body of water, it's very reminiscent of atmospheric haze, except as noted above, it doesn't concentrate around the brightest star in the cluster.

The Pleaides can fool an observer into thinking the skies are less transparent than they really are. Compare them to other nearby bright blue stars, and the nebula becomes more clear.

J


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Pleaides Nebulosity new [Re: JasonBurry]
      #5564350 - 12/10/12 03:09 PM

The nebulosity the Pleiades sits in seems to be visible to the naked eye.
Several observers one night noted that there was a glow associated with the Pleiades that was absent in the Hyades, when looking at both with the naked eye.
So, we did a few averted-vision drawings of the shape of the glow surrounding the Pleiades, and found a good match to photographic exposures that were long enough to see most of the nebulosity (REALLY long exposures show the Pleiades is toward one end of a nebula running more than 3 degrees, but I'm only talking about the nebulosity close to the stars).
I always thought the glow from the area was a little too high to be accounted for solely by the stars.
On this night, I counted 9 Pleiads, as I usually do, and one teenager up on the mountain for his astronomy class drew a map locating about 16 stars. Oh to have his eyes!

No such glow, by the way, shows up around any group of stars other than the Pleiades. Try drawing the shape of the outer edges of the glow and you'll be surprised.

As for the Merope nebula, I recall seeing it for the first time in 1963 with a 4.25" reflector. In my 12.5", it's not as "comet-shaped", but filled with striations. Such is the advantage of aperture.


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JasonBurry
sage


Reged: 04/27/12

Loc: Cape Spencer, NB, Canada
Re: Pleaides Nebulosity new [Re: Starman1]
      #5564381 - 12/10/12 03:29 PM

Yes, I'd agree with that! I've never attempted to sketch the nebulosity, but there is never a night when the sisters don't seem bathed in haze, even naked eye.

I've seen long exposure widefield shots that show that area of the sky to be extremely "dusty", from Pleaides to Hyades and beyond, great sheets and filiments of gas and dust....

J


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Dave MitskyModerator
Postmaster
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Reged: 04/08/02

Loc: PA, USA, Planet Earth
Re: Pleaides Nebulosity new [Re: JasonBurry]
      #5564403 - 12/10/12 03:48 PM

Here's one of my favorite shots. It was done with a Tele Vue NP-101is and an SBIG STL-11K camera.

M45 "The Pleiades" and IC353 + IC1995 by Tony Hallas

http://apod.nasa.gov/apod/ap071122.html


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Carol L

*****

Reged: 07/05/04

Loc: Tomahawk, WI 45N//89W
Re: Pleaides Nebulosity new [Re: blb]
      #5564698 - 12/10/12 06:43 PM

Quote:

So if you think you see the nebula, check out the Hyades and other bright stars in the neighborhood, if they do not appear to look foggy, then I guess you have seen the nebula.




You beat me to it Buddy!
I always tell folks to decide by comparison... that's the sure-fire test as far as i'm concerned.

Dave, thanks for the APOD link... what a beauty!! I hope none of the tinfoil-hat gang reads this,
but those lines in M45 bear a striking resemblance to really big contrails.


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Pleaides Nebulosity new [Re: Carol L]
      #5564710 - 12/10/12 06:55 PM

Carol,
That type of gas cloud is often referred to as "Galactic Cirrus".
Look at this deep photo of M81:
http://astrophoto.com/M81LRGBDEEP.htm
and look at how much "smoke" in the Milky Way overlaps the image of the galaxy.
When long exposures are made, it seems we see through that stuff in every direction we look.
Like this long exposure of Orion showing that all the nebulae in Orion are just bright points on one big nebula:
Orion
Or this one of M16/M17 showing they are connected:
M16/M17 I've see the bridge between them visually.

I wouldn't be surprised if a long enough exposure to the sky showed that such gas completely surrounds us. It's all a matter of how faint you go.


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Carol L

*****

Reged: 07/05/04

Loc: Tomahawk, WI 45N//89W
Re: Pleaides Nebulosity new [Re: Starman1]
      #5564860 - 12/10/12 08:38 PM

Thanks for the links and info, Don... interesting stuff!

"... such gas completely surrounds us."
You mean something like this?


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MikeBOKC
Post Laureate
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Reged: 05/10/10

Loc: Oklahoma City, OK
Re: Pleaides Nebulosity new [Re: Carol L]
      #5564950 - 12/10/12 09:37 PM

A vital and important study on the tinfoil hat issue:

http://berkeley.intel-research.net/arahimi/helmet/

I find this useful for UFO believers, bigfoot devotees and those awaiting the Mayan calendar doom moment.


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MikeRatcliff
Carpal Tunnel
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Reged: 06/12/04

Loc: Redlands, CA
Re: Pleaides Nebulosity new [Re: Starman1]
      #5565020 - 12/10/12 10:25 PM

Quote:

Or this one of M16/M17 showing they are connected:
M16/M17 I've see the bridge between them visually.






Wow, I had not heard of the bridge between M16/M17. And that it could be observed visually, double wow!


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Pleaides Nebulosity new [Re: MikeRatcliff]
      #5565262 - 12/11/12 12:53 AM

Quote:

Quote:

Or this one of M16/M17 showing they are connected:
M16/M17 I've see the bridge between them visually.






Wow, I had not heard of the bridge between M16/M17. And that it could be observed visually, double wow!



With an O-III or UHC filter.
Don


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Sasa
professor emeritus


Reged: 11/03/10

Loc: Ricany, Czech Republic
Re: Pleaides Nebulosity new [Re: Starman1]
      #5565472 - 12/11/12 07:24 AM Attachment (15 downloads)

I had always a feeling when looking at M45 that there is something wrong with my optics (like the image is behind some very fine veil). It did not occur to me until last year that I'm seeing the nebulosity which is almost everywhere. A t that time I got an idea to invert the problem. Instead of tracing nebulosity (which is almost everywhere) I started to trace the dark areas. I saw many of them and I realize that I could see on good nights nebulosity in my 80mm and 100mm refractor even from my backyard. NGC1435 then became relatively easy one. But I could trace a lot of darker features (with some dificulties). I tried to record them on paper just to compare them later with the images and to have a feeling what I actually saw (I manage to do properly only the area south of the main stars, northen part is just a quick starting sketch, I run out of time). There are definitely many brighter areas which are not simply on the images (probably some groups of stars or just trick as one tends to put the bright patches around distinguished groups of stars). But some of the features seems to be real. This year I had no luck at all, the wether was quite bad so far...

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Tony Flanders
Postmaster
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Pleaides Nebulosity new [Re: Sasa]
      #5565484 - 12/11/12 07:48 AM

Quote:

There are definitely many brighter areas which are not simply on the images (probably some groups of stars or just trick as one tends to put the bright patches around distinguished groups of stars). But some of the features seems to be real.




Looking at that sketch, it seems that the Merope Nebula is unquestionably real. The others look to me like classic connect-the-bright-dots pseudo-nebulosity. The same illusion that caused Messier to see nebulosity in M40 and M73.


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Sasa
professor emeritus


Reged: 11/03/10

Loc: Ricany, Czech Republic
Re: Pleaides Nebulosity new [Re: Tony Flanders]
      #5565508 - 12/11/12 08:15 AM

Yep, Tony, you are right. But except NGC1435, there seem to be at least one real stroke (coming from Electra), also the darker area between Merope and Electra seems to be real. The northern parts are just a quick impression drawing (as you were saying more or less connect-the-dots and atmospheric haze). My main point was that trying to trace the dark areas instead of the directly looking at nebulosity may lead to some success even from light polluted areas (my backyard is in small town just on the border of 1.5 million city).

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JIMZ7
Pooh-Bah
*****

Reged: 10/22/05

Loc: S.E.Michigan near DTW
Re: Pleaides Nebulosity new [Re: Sasa]
      #5565574 - 12/11/12 09:19 AM

Back in the mid-1960's in the city limits of Detroit it was easy to see the misty nebula in Pleaides with a homemade 6" f/4 equatorial reflector made at Polaris Telescope Shop in Dearborn Michigan. Most of the scope/mount components came from Edmund Scientific. The eyepiece used was a 20mm Erfle. Life was simple back then and the skies were much darker in the "big city".

Jim


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blb
Post Laureate


Reged: 11/25/05

Loc: Piedmont NC
Re: Pleaides Nebulosity new [Re: Tony Flanders]
      #5565977 - 12/11/12 01:44 PM

Quote:

Quote:

There are definitely many brighter areas which are not simply on the images (probably some groups of stars or just trick as one tends to put the bright patches around distinguished groups of stars). But some of the features seems to be real.




Looking at that sketch, it seems that the Merope Nebula is unquestionably real. The others look to me like classic connect-the-bright-dots pseudo-nebulosity. The same illusion that caused Messier to see nebulosity in M40 and M73.




Then please explain to me why it is on nights of good transparency/seeing that this connect-the-bright-dots pseudo-nebulosity does not appear around other bright star groups like the Hyades. When I can see it here where there is known nebulosity (with two NGC numbers) and nowhere else in that part of the sky can it be seen, is it really pseudo-nebulosity?


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Starman1
Vendor (EyepiecesEtc.com)
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Reged: 06/24/03

Loc: Los Angeles
Re: Pleaides Nebulosity new [Re: blb]
      #5566062 - 12/11/12 02:32 PM

IF you have no dew on any optical surface, and IF your optical surfaces are relatively clean, THEN seeing nebulosity around stars probably indicates there is nebulosity there.
In regard to The Pleiades, I almost always see patches of nebulosity around the stars and sections that extend well away from the stars.
I do not see that in the Perseus Double Cluster, or M35, or any other similarly-sized cluster of stars. They seem devoid of nebulosity.
There is visible nebulosity around the stars, surrounding the stars, and surrounding the cluster, that can be seen in relatively modest scopes.
What the aperture cutoff is can be determined by the altitude of the cluster, the experience of the observer, and all the same factors that influence the visibility of faint galaxies.

I find it ironic that the nebulosity is so easy in a 12.5" scope, but the view of the cluster is best in a scope like the TeleVue NP101, which doesn't show the nebula as well.


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StarStuff1
Post Laureate
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Reged: 04/01/07

Loc: South of the Mason-Dixon Line
Re: Pleaides Nebulosity new [Re: Starman1]
      #5566106 - 12/11/12 03:02 PM

Decades ago when skies were much darker I routinely saw nebulosity in M45. Nowadays it is much tougher. However, a few weeks ago I was viewing from a pretty light polluted area using a 70mm refractor working at f/2, an image intensifier eyepiece and an Orion Photographic SkyGlow filter. The nebulosity was definitely there!

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Tony Flanders
Postmaster
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Reged: 05/18/06

Loc: Cambridge, MA, USA
Re: Pleaides Nebulosity new [Re: blb]
      #5566179 - 12/11/12 03:53 PM

Quote:

Then please explain to me why it is on nights of good transparency/seeing that this connect-the-bright-dots pseudo-nebulosity does not appear around other bright star groups like the Hyades.




Because the Pleiades are brighter and tighter.

Mind you, I'm not saying that all the nebulosity is imaginary. But in this particular sketch, there's a mighty lot of it falling along nearly straight lines between bright nearby stars in places where photos show little or no nebulosity.


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markgliderpilot
member


Reged: 09/01/08

Re: Pleaides Nebulosity new [Re: Tony Flanders]
      #5566221 - 12/11/12 04:17 PM

I was looking at the Pleiades only last night. Using APM binos with 19mm panoptics fitted with dew heaters II swung across to the magnificent Pleiades star cluster, M45. This is always a stunning sight in the binoculars, a veritable field of brilliant diamonds with chains of fainter stars radiating in all directions.  There is also some faint nebulosity within the Pleiades, the left over dust and gas from when this cluster was born.  I am always sceptical when I can see the faint glow around the brighter stars from a light polluted site such as my small town observatory.  While it could be the nebulosity, it is more likely to be a faint fogging of the optics or the glow from any atmospheric humidity lit up by the streetlights.  Although it was a very transparent night, there was clearly some mist about so the heaters were on keeping the optics free from dew. 
 
It was with these thoughts in mind that I studied the glow around the brighter stars.  After a few minutes I noticed very dark “ink spots” between the stars.  It was with a thrill that I realised that I was indeed picking out the faint nebulosity and noticing its contrast with the black background sky.  I will now have to make a detailed sketch of this wonderful cluster including the nebulosity from home and our dark sky site.

Best regards

Mark


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Jeremy Perez
Carpal Tunnel
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Reged: 08/12/04

Loc: Flagstaff, Arizona, USA
Re: Pleaides Nebulosity new [Re: markgliderpilot]
      #5566259 - 12/11/12 04:40 PM

I spent a couple evenings over the weekend observing and sketching the Pleiades naked eye and through 15 x 70 binoculars. The Merope nebula was the only one I could confidently detect with binoculars--its brightness and asymmetry really seem to do the trick for visibility. Overall though, I'm cautious about the appearance of nebulosity that seems to engulf the cluster. It definitely appears that way! However, I just don't think my equipment and my eyes are up to the task of sorting glare from nebulosity at those scales.

To pull on what Tony said, in my personal experience, the combination of magnitude and tight grouping in the Pleiades doesn't compare well to other clusters (such as the Hyades and Double Cluster). So I don't feel I can rely on those as a baseline. The combined, overlapping glare of all those bright stars so close to one another just seems to have a unique, overpowering effect. With that said, if I were to make some decisive upgrades to my choice of binoculars, perhaps I could cross a glare threshold there. As for naked eye, my overcorrected stargazing glasses are as good as it gets, and I can't convince myself that the amazing, hazy glow isn't simply combined glare from the bright members and perhaps integrated light from the other fainter, embedded and surrounding stars.

I still need to go back and do a closer telescopic study and see what I can pull out at higher magnifications!


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